The invention describes novel compounds of the formula I which are biologically active as ligands of integrin &agr;v&bgr;3
X—Y—Z—R1—CH2—R2(R4)—CH2—CO—R5
in which X, Y, Z, R1, R2, R4 and R5 are as defined in claim 1, and their physiologically acceptable salts and solvates.